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                    1.1：移动开发技术简介
            
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                    1.2：初识Flutter
            
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                    1.3：搭建Flutter开发环境
            
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                    1.4：Dart语言简介
            
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                    第二章：第一个Flutter应用
            
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                    2.1：计数器示例
            
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                    2.2：路由管理
            
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                    2.4：资源管理
            
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                    2.5：调试Flutter APP
            
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                    2.6：Dart线程模型及异常捕获
            
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                    第三章：基础组件
            
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                    3.1：Widget简介
            
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                    3.2：状态管理
            
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                    3.3：文本、字体样式
            
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                    3.4：按钮
            
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                    3.5：图片和Icon
            
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                    3.6：单选框和复选框
            
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                    3.7：输入框和表单
            
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                    3.8：进度指示器
            
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                    第四章：布局类组件
            
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                    4.1：布局类组件简介
            
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                    4.2：线性布局（Row、Column）
            
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                    4.3：弹性布局（Flex）
            
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                    4.4：流式布局（Wrap、Flow）
            
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                    4.5：层叠布局（Stack、Positioned）
            
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                    4.6：对齐与相对定位（Align）
            
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                    第五章：容器类组件
            
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                    5.1：填充（Padding）
            
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                    5.2：尺寸限制类容器（ConstrainedBox等）
            
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                    5.3：装饰容器（DecoratedBox）
            
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                    5.4：变换（Transform）
            
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                    5.5：Container容器
            
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                    5.6：Scaffold、TabBar、底部导航
            
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                    5.7：剪裁（Clip）
            
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        <li class="chapter " data-level="2.6" data-path="../chapter6/">
            
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                    第六章：可滚动组件
            
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        <li class="chapter " data-level="2.6.1" data-path="../chapter6/intro.html">
            
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                    6.1：可滚动组件简介
            
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        <li class="chapter " data-level="2.6.2" data-path="../chapter6/single_child_scrollview.html">
            
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                    6.2：SingleChildScrollView
            
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                    6.3：ListView
            
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                    6.4：GridView
            
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                    6.5：CustomScrollView
            
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                    6.6：滚动监听及控制（ScrollController）
            
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                    第七章：功能型组件
            
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                    7.1：导航返回拦截（WillPopScope）
            
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                    7.2：数据共享（InheritedWidget）
            
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                    7.3： 跨组件状态共享（Provider）
            
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                    7.4：颜色和主题（Theme）
            
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                    7.5：异步UI更新（FutureBuilder、StreamBuilder）
            
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        <li class="chapter " data-level="2.7.6" data-path="../chapter7/dailog.html">
            
                <a href="../chapter7/dailog.html">
            
                    
                    7.6：对话框详解
            
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        <li class="header">进阶篇</li>
        
        
    
        <li class="chapter " data-level="3.1" data-path="../chapter8/">
            
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                    第八章：事件处理与通知
            
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        <li class="chapter " data-level="3.1.1" data-path="../chapter8/listener.html">
            
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                    8.1：原始指针事件处理
            
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        <li class="chapter " data-level="3.1.2" data-path="../chapter8/gesture.html">
            
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                    8.2：手势识别
            
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        <li class="chapter " data-level="3.1.3" data-path="../chapter8/eventbus.html">
            
                <a href="../chapter8/eventbus.html">
            
                    
                    8.3：全局事件总线
            
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        <li class="chapter " data-level="3.1.4" data-path="../chapter8/notification.html">
            
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                    8.4：通知(Notification)
            
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        <li class="chapter " data-level="3.2" data-path="../chapter9/">
            
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                    第九章：动画
            
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        <li class="chapter " data-level="3.2.1" data-path="../chapter9/intro.html">
            
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                    9.1：Flutter动画简介
            
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        <li class="chapter " data-level="3.2.2" data-path="../chapter9/animation_structure.html">
            
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                    9.2：动画结构
            
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        <li class="chapter " data-level="3.2.3" data-path="../chapter9/route_transition.html">
            
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                    9.3：自定义路由过渡动画
            
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        <li class="chapter " data-level="3.2.4" data-path="../chapter9/hero.html">
            
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                    9.4：Hero动画
            
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                    9.5：交织动画
            
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        <li class="chapter " data-level="3.2.6" data-path="../chapter9/animated_switcher.html">
            
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                    9.6：通用“动画切换”组件（AnimatedSwitcher）
            
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        <li class="chapter " data-level="3.2.7" data-path="../chapter9/animated_widgets.html">
            
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                    9.7：动画过渡组件
            
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        </li>
    
        <li class="chapter " data-level="3.3" data-path="../chapter10/">
            
                <a href="../chapter10/">
            
                    
                    第十章：自定义组件
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.3.1" data-path="../chapter10/intro.html">
            
                <a href="../chapter10/intro.html">
            
                    
                    10.1：自定义组件方法简介
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.2" data-path="../chapter10/combine.html">
            
                <a href="../chapter10/combine.html">
            
                    
                    10.2：组合现有组件
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.3" data-path="../chapter10/turn_box.html">
            
                <a href="../chapter10/turn_box.html">
            
                    
                    10.3：组合实例：TurnBox
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.4" data-path="../chapter10/custom_paint.html">
            
                <a href="../chapter10/custom_paint.html">
            
                    
                    10.4：自绘组件（CustomPaint与Canvas）
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.5" data-path="../chapter10/gradient_circular_progress_demo.html">
            
                <a href="../chapter10/gradient_circular_progress_demo.html">
            
                    
                    10.5：自绘实例：圆形渐变进度条(自绘)
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.4" data-path="../chapter11/">
            
                <a href="../chapter11/">
            
                    
                    第十一章：文件操作与网络请求
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.4.1" data-path="../chapter11/file_operation.html">
            
                <a href="../chapter11/file_operation.html">
            
                    
                    11.1：文件操作
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.4.2" data-path="../chapter11/http.html">
            
                <a href="../chapter11/http.html">
            
                    
                    11.2：Http请求-HttpClient
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.4.3" data-path="../chapter11/dio.html">
            
                <a href="../chapter11/dio.html">
            
                    
                    11.3：Http请求-Dio package
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.4.4" data-path="../chapter11/download_with_chunks.html">
            
                <a href="../chapter11/download_with_chunks.html">
            
                    
                    11.4：实例：Http分块下载
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.4.5" data-path="../chapter11/websocket.html">
            
                <a href="../chapter11/websocket.html">
            
                    
                    11.5：WebSocket
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.4.6" data-path="../chapter11/socket.html">
            
                <a href="../chapter11/socket.html">
            
                    
                    11.6：使用Socket API
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.4.7" data-path="../chapter11/json_model.html">
            
                <a href="../chapter11/json_model.html">
            
                    
                    11.7：Json转Dart Model类
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.5" data-path="../chapter12/">
            
                <a href="../chapter12/">
            
                    
                    第十二章：包与插件
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.5.1" data-path="../chapter12/develop_package.html">
            
                <a href="../chapter12/develop_package.html">
            
                    
                    12.1：开发package
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.5.2" data-path="../chapter12/platform-channel.html">
            
                <a href="../chapter12/platform-channel.html">
            
                    
                    12.2：平台通道简介
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.5.3" data-path="../chapter12/develop_plugin.html">
            
                <a href="../chapter12/develop_plugin.html">
            
                    
                    12.3：开发Flutter插件
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.5.4" data-path="../chapter12/android_implement.html">
            
                <a href="../chapter12/android_implement.html">
            
                    
                    12.4：插件开发：实现Android端API
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.5.5" data-path="../chapter12/ios_implement.html">
            
                <a href="../chapter12/ios_implement.html">
            
                    
                    12.5：插件开发：实现IOS端API
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.5.6" data-path="../chapter12/texture_platformview.html">
            
                <a href="../chapter12/texture_platformview.html">
            
                    
                    12.6：Texture和PlatformView
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.6" data-path="../chapter13/">
            
                <a href="../chapter13/">
            
                    
                    第十三章：国际化
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.6.1" data-path="../chapter13/multi_languages_support.html">
            
                <a href="../chapter13/multi_languages_support.html">
            
                    
                    13.1：让App支持多语言
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.6.2" data-path="../chapter13/locallization_implement.html">
            
                <a href="../chapter13/locallization_implement.html">
            
                    
                    13.2：实现Localizations
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.6.3" data-path="../chapter13/intl.html">
            
                <a href="../chapter13/intl.html">
            
                    
                    13.3：使用Intl包
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.6.4" data-path="../chapter13/faq.html">
            
                <a href="../chapter13/faq.html">
            
                    
                    13.4：国际化常见问题
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.7" data-path="../chapter14/">
            
                <a href="../chapter14/">
            
                    
                    第十四章：Flutter核心原理
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.7.1" data-path="../chapter14/flutter_ui_system.html">
            
                <a href="../chapter14/flutter_ui_system.html">
            
                    
                    14.1：Flutter UI系统
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.7.2" data-path="../chapter14/element_buildcontext.html">
            
                <a href="../chapter14/element_buildcontext.html">
            
                    
                    14.2：Element和BuildContext
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.7.3" data-path="../chapter14/render_object.html">
            
                <a href="../chapter14/render_object.html">
            
                    
                    14.3：RenderObject与RenderBox
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.7.4" data-path="../chapter14/flutter_app_startup.html">
            
                <a href="../chapter14/flutter_app_startup.html">
            
                    
                    14.4：Flutter从启动到显示
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.7.5" data-path="../chapter14/image_and_cache.html">
            
                <a href="../chapter14/image_and_cache.html">
            
                    
                    14.5：Flutter图片加载与缓存
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    

    
        
        <li class="header">实例篇</li>
        
        
    
        <li class="chapter " data-level="4.1" data-path="../chapter15/intro.html">
            
                <a href="../chapter15/intro.html">
            
                    
                    第十五章：一个完整的Flutter应用
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="4.1.1" data-path="../chapter15/intro.html">
            
                <a href="../chapter15/intro.html">
            
                    
                    15.1：应用简介
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="4.1.2" data-path="../chapter15/code_structure.html">
            
                <a href="../chapter15/code_structure.html">
            
                    
                    15.2：APP代码结构
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="4.1.3" data-path="../chapter15/models.html">
            
                <a href="../chapter15/models.html">
            
                    
                    15.3：Model类定义
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="4.1.4" data-path="../chapter15/globals.html">
            
                <a href="../chapter15/globals.html">
            
                    
                    15.4：全局变量及共享状态
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="4.1.5" data-path="../chapter15/network.html">
            
                <a href="../chapter15/network.html">
            
                    
                    15.5：网络请求封装
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="4.1.6" data-path="../chapter15/entry.html">
            
                <a href="../chapter15/entry.html">
            
                    
                    15.6：App入口及首页
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="4.1.7" data-path="../chapter15/login_page.html">
            
                <a href="../chapter15/login_page.html">
            
                    
                    15.7：登录页
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="4.1.8" data-path="../chapter15/language_and_theme_setting.html">
            
                <a href="../chapter15/language_and_theme_setting.html">
            
                    
                    15.8：多语言和多主题
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    

    

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                                <h1 id="21-&#x8BA1;&#x6570;&#x5668;&#x5E94;&#x7528;&#x793A;&#x4F8B;">2.1 &#x8BA1;&#x6570;&#x5668;&#x5E94;&#x7528;&#x793A;&#x4F8B;</h1>
<p>&#x7528;Android Studio&#x548C;VS Code&#x521B;&#x5EFA;&#x7684;Flutter&#x5E94;&#x7528;&#x6A21;&#x677F;&#x9ED8;&#x8BA4;&#x662F;&#x4E00;&#x4E2A;&#x7B80;&#x5355;&#x7684;&#x8BA1;&#x6570;&#x5668;&#x793A;&#x4F8B;&#x3002;&#x672C;&#x8282;&#x5148;&#x4ED4;&#x7EC6;&#x8BB2;&#x89E3;&#x4E00;&#x4E0B;&#x8FD9;&#x4E2A;&#x8BA1;&#x6570;&#x5668;Demo&#x7684;&#x6E90;&#x7801;&#xFF0C;&#x8BA9;&#x8BFB;&#x8005;&#x5BF9;Flutter&#x5E94;&#x7528;&#x7A0B;&#x5E8F;&#x7ED3;&#x6784;&#x6709;&#x4E2A;&#x57FA;&#x672C;&#x4E86;&#x89E3;&#xFF0C;&#x7136;&#x540E;&#x5728;&#x968F;&#x540E;&#x7684;&#x5C0F;&#x8282;&#x4E2D;&#x5C06;&#x4F1A;&#x57FA;&#x4E8E;&#x6B64;&#x793A;&#x4F8B;&#xFF0C;&#x4E00;&#x6B65;&#x4E00;&#x6B65;&#x6DFB;&#x52A0;&#x4E00;&#x4E9B;&#x65B0;&#x7684;&#x529F;&#x80FD;&#x6765;&#x4ECB;&#x7ECD;Flutter&#x5E94;&#x7528;&#x7684;&#x5176;&#x5B83;&#x6982;&#x5FF5;&#x4E0E;&#x6280;&#x672F;&#x3002;</p>
<p>&#x5BF9;&#x4E8E;&#x63A5;&#x4E0B;&#x6765;&#x7684;&#x793A;&#x4F8B;&#xFF0C;&#x5E0C;&#x671B;&#x8BFB;&#x8005;&#x53EF;&#x4EE5;&#x8DDF;&#x7740;&#x7B14;&#x8005;&#x4E00;&#x8D77;&#x4EB2;&#x81EA;&#x52A8;&#x624B;&#x6765;&#x5199;&#x4E00;&#x4E0B;&#xFF0C;&#x8FD9;&#x6837;&#x4E0D;&#x4EC5;&#x53EF;&#x4EE5;&#x52A0;&#x6DF1;&#x5370;&#x8C61;&#xFF0C;&#x800C;&#x4E14;&#x4E5F;&#x4F1A;&#x5BF9;&#x4ECB;&#x7ECD;&#x7684;&#x6982;&#x5FF5;&#x4E0E;&#x6280;&#x672F;&#x6709;&#x4E00;&#x4E2A;&#x771F;&#x5207;&#x7684;&#x4F53;&#x4F1A;&#x3002;&#x5982;&#x679C;&#x4F60;&#x8FD8;&#x4E0D;&#x662F;&#x5F88;&#x719F;&#x6089;Dart&#x8BED;&#x8A00;&#x6216;&#x8005;&#x6CA1;&#x6709;&#x79FB;&#x52A8;&#x5F00;&#x53D1;&#x7ECF;&#x9A8C;&#xFF0C;&#x4E0D;&#x7528;&#x62C5;&#x5FC3;&#xFF0C;&#x53EA;&#x8981;&#x4F60;&#x719F;&#x6089;&#x9762;&#x5411;&#x5BF9;&#x8C61;&#x548C;&#x57FA;&#x672C;&#x7F16;&#x7A0B;&#x6982;&#x5FF5;&#xFF08;&#x5982;&#x53D8;&#x91CF;&#x3001;&#x5FAA;&#x73AF;&#x548C;&#x6761;&#x4EF6;&#x63A7;&#x5236;&#xFF09;&#xFF0C;&#x5219;&#x53EF;&#x4EE5;&#x5B8C;&#x6210;&#x672C;&#x793A;&#x4F8B;&#x3002;</p>
<h2 id="211-&#x521B;&#x5EFA;flutter&#x5E94;&#x7528;&#x6A21;&#x677F;">2.1.1 &#x521B;&#x5EFA;Flutter&#x5E94;&#x7528;&#x6A21;&#x677F;</h2>
<p>&#x901A;&#x8FC7;Android Studio&#x6216;VS Code&#x521B;&#x5EFA;&#x4E00;&#x4E2A;&#x65B0;&#x7684;Flutter&#x5DE5;&#x7A0B;&#xFF0C;&#x547D;&#x540D;&#x4E3A;&quot;first_flutter_app&quot;&#x3002;&#x521B;&#x5EFA;&#x597D;&#x540E;&#xFF0C;&#x5C31;&#x4F1A;&#x5F97;&#x5230;&#x4E00;&#x4E2A;&#x8BA1;&#x6570;&#x5668;&#x5E94;&#x7528;&#x7684;Demo&#x3002;</p>
<blockquote>
<p>&#x6CE8;&#x610F;&#xFF0C;&#x9ED8;&#x8BA4;Demo&#x793A;&#x4F8B;&#x53EF;&#x80FD;&#x968F;&#x7740;&#x7F16;&#x8F91;&#x5668;Flutter&#x63D2;&#x4EF6;&#x7684;&#x7248;&#x672C;&#x53D8;&#x5316;&#x800C;&#x53D8;&#x5316;&#xFF0C;&#x672C;&#x4F8B;&#x4E2D;&#x4F1A;&#x4ECB;&#x7ECD;&#x8BA1;&#x6570;&#x5668;&#x793A;&#x4F8B;&#x7684;&#x5168;&#x90E8;&#x4EE3;&#x7801;&#xFF0C;&#x6240;&#x4EE5;&#x4E0D;&#x4F1A;&#x5BF9;&#x672C;&#x793A;&#x4F8B;&#x4EA7;&#x751F;&#x5F71;&#x54CD;&#x3002;</p>
</blockquote>
<p>&#x6211;&#x4EEC;&#x5148;&#x8FD0;&#x884C;&#x521B;&#x5EFA;&#x7684;&#x5DE5;&#x7A0B;&#xFF0C;&#x6548;&#x679C;&#x5982;&#x56FE;2-1&#x6240;&#x793A;&#xFF1A;</p>
<p><img src="https://pcdn.flutterchina.club/imgs/2-1.png" alt="&#x56FE;2-1"></p>
<p>&#x8BE5;&#x8BA1;&#x6570;&#x5668;&#x793A;&#x4F8B;&#x4E2D;&#xFF0C;&#x6BCF;&#x70B9;&#x51FB;&#x4E00;&#x6B21;&#x53F3;&#x4E0B;&#x89D2;&#x5E26;&#x201C;+&#x201D;&#x53F7;&#x7684;&#x60AC;&#x6D6E;&#x6309;&#x94AE;&#xFF0C;&#x5C4F;&#x5E55;&#x4E2D;&#x592E;&#x7684;&#x6570;&#x5B57;&#x5C31;&#x4F1A;&#x52A0;1&#x3002;</p>
<p>&#x5728;&#x8FD9;&#x4E2A;&#x793A;&#x4F8B;&#x4E2D;&#xFF0C;&#x4E3B;&#x8981;Dart&#x4EE3;&#x7801;&#x662F;&#x5728; <strong>lib/main.dart</strong> &#x6587;&#x4EF6;&#x4E2D;&#xFF0C;&#x4E0B;&#x9762;&#x662F;&#x5B83;&#x7684;&#x6E90;&#x7801;&#xFF1A;</p>
<pre class="language-"><code class="lang-dart"><span class="token keyword">import</span> <span class="token string">&apos;package:flutter/material.dart&apos;</span><span class="token punctuation">;</span>

<span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=</span><span class="token operator">&gt;</span> <span class="token function">runApp</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">MyApp</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">class</span> <span class="token class-name">MyApp</span> <span class="token keyword">extends</span> <span class="token class-name">StatelessWidget</span> <span class="token punctuation">{</span>
  <span class="token metadata symbol">@override</span>
  Widget <span class="token function">build</span><span class="token punctuation">(</span>BuildContext context<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> <span class="token keyword">new</span> <span class="token class-name">MaterialApp</span><span class="token punctuation">(</span>
      title<span class="token punctuation">:</span> <span class="token string">&apos;Flutter Demo&apos;</span><span class="token punctuation">,</span>
      theme<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">ThemeData</span><span class="token punctuation">(</span>
        primarySwatch<span class="token punctuation">:</span> Colors<span class="token punctuation">.</span>blue<span class="token punctuation">,</span>
      <span class="token punctuation">)</span><span class="token punctuation">,</span>
      home<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">MyHomePage</span><span class="token punctuation">(</span>title<span class="token punctuation">:</span> <span class="token string">&apos;Flutter Demo Home Page&apos;</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
    <span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

<span class="token keyword">class</span> <span class="token class-name">MyHomePage</span> <span class="token keyword">extends</span> <span class="token class-name">StatefulWidget</span> <span class="token punctuation">{</span>
  <span class="token function">MyHomePage</span><span class="token punctuation">(</span><span class="token punctuation">{</span>Key key<span class="token punctuation">,</span> <span class="token keyword">this</span><span class="token punctuation">.</span>title<span class="token punctuation">}</span><span class="token punctuation">)</span> <span class="token punctuation">:</span> <span class="token keyword">super</span><span class="token punctuation">(</span>key<span class="token punctuation">:</span> key<span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token keyword">final</span> String title<span class="token punctuation">;</span>

  <span class="token metadata symbol">@override</span>
  _MyHomePageState <span class="token function">createState</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=</span><span class="token operator">&gt;</span> <span class="token keyword">new</span> <span class="token class-name">_MyHomePageState</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token keyword">class</span> <span class="token class-name">_MyHomePageState</span> <span class="token keyword">extends</span> <span class="token class-name">State</span><span class="token operator">&lt;</span>MyHomePage<span class="token operator">&gt;</span> <span class="token punctuation">{</span>
  int _counter <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>

  <span class="token keyword">void</span> <span class="token function">_incrementCounter</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token function">setState</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
      _counter<span class="token operator">++</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>

  <span class="token metadata symbol">@override</span>
  Widget <span class="token function">build</span><span class="token punctuation">(</span>BuildContext context<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> <span class="token keyword">new</span> <span class="token class-name">Scaffold</span><span class="token punctuation">(</span>
      appBar<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">AppBar</span><span class="token punctuation">(</span>
        title<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">Text</span><span class="token punctuation">(</span>widget<span class="token punctuation">.</span>title<span class="token punctuation">)</span><span class="token punctuation">,</span>
      <span class="token punctuation">)</span><span class="token punctuation">,</span>
      body<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">Center</span><span class="token punctuation">(</span>
        child<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">Column</span><span class="token punctuation">(</span>
          mainAxisAlignment<span class="token punctuation">:</span> MainAxisAlignment<span class="token punctuation">.</span>center<span class="token punctuation">,</span>
          children<span class="token punctuation">:</span> <span class="token operator">&lt;</span>Widget<span class="token operator">&gt;</span><span class="token punctuation">[</span>
            <span class="token keyword">new</span> <span class="token class-name">Text</span><span class="token punctuation">(</span>
              <span class="token string">&apos;You have pushed the button this many times:&apos;</span><span class="token punctuation">,</span>
            <span class="token punctuation">)</span><span class="token punctuation">,</span>
            <span class="token keyword">new</span> <span class="token class-name">Text</span><span class="token punctuation">(</span>
              <span class="token string">&apos;$_counter&apos;</span><span class="token punctuation">,</span>
              style<span class="token punctuation">:</span> Theme<span class="token punctuation">.</span><span class="token function">of</span><span class="token punctuation">(</span>context<span class="token punctuation">)</span><span class="token punctuation">.</span>textTheme<span class="token punctuation">.</span>display1<span class="token punctuation">,</span>
            <span class="token punctuation">)</span><span class="token punctuation">,</span>
          <span class="token punctuation">]</span><span class="token punctuation">,</span>
        <span class="token punctuation">)</span><span class="token punctuation">,</span>
      <span class="token punctuation">)</span><span class="token punctuation">,</span>
      floatingActionButton<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">FloatingActionButton</span><span class="token punctuation">(</span>
        onPressed<span class="token punctuation">:</span> _incrementCounter<span class="token punctuation">,</span>
        tooltip<span class="token punctuation">:</span> <span class="token string">&apos;Increment&apos;</span><span class="token punctuation">,</span>
        child<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">Icon</span><span class="token punctuation">(</span>Icons<span class="token punctuation">.</span>add<span class="token punctuation">)</span><span class="token punctuation">,</span>
      <span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token comment">// This trailing comma makes auto-formatting nicer for build methods.</span>
    <span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre>
<h3 id="&#x5206;&#x6790;">&#x5206;&#x6790;</h3>
<ol>
<li><p>&#x5BFC;&#x5165;&#x5305;&#x3002;</p>
<pre class="language-"><code class="lang-dart"><span class="token keyword">import</span> <span class="token string">&apos;package:flutter/material.dart&apos;</span><span class="token punctuation">;</span>
</code></pre>
<p>&#x6B64;&#x884C;&#x4EE3;&#x7801;&#x4F5C;&#x7528;&#x662F;&#x5BFC;&#x5165;&#x4E86;Material UI&#x7EC4;&#x4EF6;&#x5E93;&#x3002;<a href="https://material.io/guidelines/" target="_blank">Material</a>&#x662F;&#x4E00;&#x79CD;&#x6807;&#x51C6;&#x7684;&#x79FB;&#x52A8;&#x7AEF;&#x548C;web&#x7AEF;&#x7684;&#x89C6;&#x89C9;&#x8BBE;&#x8BA1;&#x8BED;&#x8A00;&#xFF0C; Flutter&#x9ED8;&#x8BA4;&#x63D0;&#x4F9B;&#x4E86;&#x4E00;&#x5957;&#x4E30;&#x5BCC;&#x7684;Material&#x98CE;&#x683C;&#x7684;UI&#x7EC4;&#x4EF6;&#x3002;</p>
</li>
<li><p>&#x5E94;&#x7528;&#x5165;&#x53E3;&#x3002;</p>
<pre class="language-"><code class="lang-dart"><span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=</span><span class="token operator">&gt;</span> <span class="token function">runApp</span><span class="token punctuation">(</span><span class="token function">MyApp</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre>
<ul>
<li>&#x4E0E;C/C++&#x3001;Java&#x7C7B;&#x4F3C;&#xFF0C;Flutter &#x5E94;&#x7528;&#x4E2D;<code>main</code>&#x51FD;&#x6570;&#x4E3A;&#x5E94;&#x7528;&#x7A0B;&#x5E8F;&#x7684;&#x5165;&#x53E3;&#x3002;<code>main</code>&#x51FD;&#x6570;&#x4E2D;&#x8C03;&#x7528;&#x4E86;<code>runApp</code> &#x65B9;&#x6CD5;&#xFF0C;&#x5B83;&#x7684;&#x529F;&#x80FD;&#x662F;&#x542F;&#x52A8;Flutter&#x5E94;&#x7528;&#x3002;<code>runApp</code>&#x5B83;&#x63A5;&#x53D7;&#x4E00;&#x4E2A;<code>Widget</code>&#x53C2;&#x6570;&#xFF0C;&#x5728;&#x672C;&#x793A;&#x4F8B;&#x4E2D;&#x5B83;&#x662F;&#x4E00;&#x4E2A;<code>MyApp</code>&#x5BF9;&#x8C61;&#xFF0C;<code>MyApp()</code>&#x662F;Flutter&#x5E94;&#x7528;&#x7684;&#x6839;&#x7EC4;&#x4EF6;&#x3002;</li>
<li><code>main</code>&#x51FD;&#x6570;&#x4F7F;&#x7528;&#x4E86;(<code>=&gt;</code>)&#x7B26;&#x53F7;&#xFF0C;&#x8FD9;&#x662F;Dart&#x4E2D;&#x5355;&#x884C;&#x51FD;&#x6570;&#x6216;&#x65B9;&#x6CD5;&#x7684;&#x7B80;&#x5199;&#x3002;</li>
</ul>
</li>
<li><p>&#x5E94;&#x7528;&#x7ED3;&#x6784;&#x3002;</p>
<pre class="language-"><code class="lang-dart"><span class="token keyword">class</span> <span class="token class-name">MyApp</span> <span class="token keyword">extends</span> <span class="token class-name">StatelessWidget</span> <span class="token punctuation">{</span>
  <span class="token metadata symbol">@override</span>
  Widget <span class="token function">build</span><span class="token punctuation">(</span>BuildContext context<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> <span class="token keyword">new</span> <span class="token class-name">MaterialApp</span><span class="token punctuation">(</span>
      <span class="token comment">//&#x5E94;&#x7528;&#x540D;&#x79F0;  </span>
      title<span class="token punctuation">:</span> <span class="token string">&apos;Flutter Demo&apos;</span><span class="token punctuation">,</span> 
      theme<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">ThemeData</span><span class="token punctuation">(</span>
        <span class="token comment">//&#x84DD;&#x8272;&#x4E3B;&#x9898;  </span>
        primarySwatch<span class="token punctuation">:</span> Colors<span class="token punctuation">.</span>blue<span class="token punctuation">,</span>
      <span class="token punctuation">)</span><span class="token punctuation">,</span>
      <span class="token comment">//&#x5E94;&#x7528;&#x9996;&#x9875;&#x8DEF;&#x7531;  </span>
      home<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">MyHomePage</span><span class="token punctuation">(</span>title<span class="token punctuation">:</span> <span class="token string">&apos;Flutter Demo Home Page&apos;</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
    <span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre>
<ul>
<li><p><code>MyApp</code>&#x7C7B;&#x4EE3;&#x8868;Flutter&#x5E94;&#x7528;&#xFF0C;&#x5B83;&#x7EE7;&#x627F;&#x4E86; <code>StatelessWidget</code>&#x7C7B;&#xFF0C;&#x8FD9;&#x4E5F;&#x5C31;&#x610F;&#x5473;&#x7740;&#x5E94;&#x7528;&#x672C;&#x8EAB;&#x4E5F;&#x662F;&#x4E00;&#x4E2A;widget&#x3002;</p>
</li>
<li><p>&#x5728;Flutter&#x4E2D;&#xFF0C;&#x5927;&#x591A;&#x6570;&#x4E1C;&#x897F;&#x90FD;&#x662F;widget&#xFF08;&#x540E;&#x540C;&#x201C;&#x7EC4;&#x4EF6;&#x201D;&#x6216;&#x201C;&#x90E8;&#x4EF6;&#x201D;&#xFF09;&#xFF0C;&#x5305;&#x62EC;&#x5BF9;&#x9F50;(alignment)&#x3001;&#x586B;&#x5145;(padding)&#x548C;&#x5E03;&#x5C40;(layout)&#x7B49;&#xFF0C;&#x5B83;&#x4EEC;&#x90FD;&#x662F;&#x4EE5;widget&#x7684;&#x5F62;&#x5F0F;&#x63D0;&#x4F9B;&#x3002;</p>
</li>
<li><p>Flutter&#x5728;&#x6784;&#x5EFA;&#x9875;&#x9762;&#x65F6;&#xFF0C;&#x4F1A;&#x8C03;&#x7528;&#x7EC4;&#x4EF6;&#x7684;<code>build</code>&#x65B9;&#x6CD5;&#xFF0C;widget&#x7684;&#x4E3B;&#x8981;&#x5DE5;&#x4F5C;&#x662F;&#x63D0;&#x4F9B;&#x4E00;&#x4E2A;build()&#x65B9;&#x6CD5;&#x6765;&#x63CF;&#x8FF0;&#x5982;&#x4F55;&#x6784;&#x5EFA;UI&#x754C;&#x9762;&#xFF08;&#x901A;&#x5E38;&#x662F;&#x901A;&#x8FC7;&#x7EC4;&#x5408;&#x3001;&#x62FC;&#x88C5;&#x5176;&#x5B83;&#x57FA;&#x7840;widget&#xFF09;&#x3002;</p>
</li>
<li><p><code>MaterialApp</code> &#x662F;Material&#x5E93;&#x4E2D;&#x63D0;&#x4F9B;&#x7684;Flutter APP&#x6846;&#x67B6;&#xFF0C;&#x901A;&#x8FC7;&#x5B83;&#x53EF;&#x4EE5;&#x8BBE;&#x7F6E;&#x5E94;&#x7528;&#x7684;&#x540D;&#x79F0;&#x3001;&#x4E3B;&#x9898;&#x3001;&#x8BED;&#x8A00;&#x3001;&#x9996;&#x9875;&#x53CA;&#x8DEF;&#x7531;&#x5217;&#x8868;&#x7B49;&#x3002;<code>MaterialApp</code>&#x4E5F;&#x662F;&#x4E00;&#x4E2A;widget&#x3002;</p>
</li>
<li><p><code>home</code> &#x4E3A;Flutter&#x5E94;&#x7528;&#x7684;&#x9996;&#x9875;&#xFF0C;&#x5B83;&#x4E5F;&#x662F;&#x4E00;&#x4E2A;widget&#x3002;</p>
</li>
</ul>
</li>
</ol>
<h2 id="212-&#x9996;&#x9875;">2.1.2 &#x9996;&#x9875;</h2>
<pre class="language-"><code class="lang-dart">   <span class="token keyword">class</span> <span class="token class-name">MyHomePage</span> <span class="token keyword">extends</span> <span class="token class-name">StatefulWidget</span> <span class="token punctuation">{</span>
     <span class="token function">MyHomePage</span><span class="token punctuation">(</span><span class="token punctuation">{</span>Key key<span class="token punctuation">,</span> <span class="token keyword">this</span><span class="token punctuation">.</span>title<span class="token punctuation">}</span><span class="token punctuation">)</span> <span class="token punctuation">:</span> <span class="token keyword">super</span><span class="token punctuation">(</span>key<span class="token punctuation">:</span> key<span class="token punctuation">)</span><span class="token punctuation">;</span>
     <span class="token keyword">final</span> String title<span class="token punctuation">;</span>
     <span class="token metadata symbol">@override</span>
     _MyHomePageState <span class="token function">createState</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=</span><span class="token operator">&gt;</span> <span class="token keyword">new</span> <span class="token class-name">_MyHomePageState</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
   <span class="token punctuation">}</span>

   <span class="token keyword">class</span> <span class="token class-name">_MyHomePageState</span> <span class="token keyword">extends</span> <span class="token class-name">State</span><span class="token operator">&lt;</span>MyHomePage<span class="token operator">&gt;</span> <span class="token punctuation">{</span>
    <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
   <span class="token punctuation">}</span>
</code></pre>
<p><code>MyHomePage</code> &#x662F;Flutter&#x5E94;&#x7528;&#x7684;&#x9996;&#x9875;&#xFF0C;&#x5B83;&#x7EE7;&#x627F;&#x81EA;<code>StatefulWidget</code>&#x7C7B;&#xFF0C;&#x8868;&#x793A;&#x5B83;&#x662F;&#x4E00;&#x4E2A;&#x6709;&#x72B6;&#x6001;&#x7684;&#x7EC4;&#x4EF6;&#xFF08;Stateful widget&#xFF09;&#x3002;&#x5173;&#x4E8E;Stateful widget&#x6211;&#x4EEC;&#x5C06;&#x5728;&#x7B2C;&#x4E09;&#x7AE0;&#x201C;Widget&#x7B80;&#x4ECB;&#x201D;&#x4E00;&#x8282;&#x4ED4;&#x7EC6;&#x4ECB;&#x7ECD;&#xFF0C;&#x73B0;&#x5728;&#x6211;&#x4EEC;&#x53EA;&#x9700;&#x7B80;&#x5355;&#x8BA4;&#x4E3A;&#x6709;&#x72B6;&#x6001;&#x7684;&#x7EC4;&#x4EF6;&#xFF08;Stateful widget&#xFF09; &#x548C;&#x65E0;&#x72B6;&#x6001;&#x7684;&#x7EC4;&#x4EF6;&#xFF08;Stateless widget&#xFF09;&#x6709;&#x4E24;&#x70B9;&#x4E0D;&#x540C;&#xFF1A;</p>
<ol>
<li><p>Stateful widget&#x53EF;&#x4EE5;&#x62E5;&#x6709;&#x72B6;&#x6001;&#xFF0C;&#x8FD9;&#x4E9B;&#x72B6;&#x6001;&#x5728;widget&#x751F;&#x547D;&#x5468;&#x671F;&#x4E2D;&#x662F;&#x53EF;&#x4EE5;&#x53D8;&#x7684;&#xFF0C;&#x800C;Stateless widget&#x662F;&#x4E0D;&#x53EF;&#x53D8;&#x7684;&#x3002;</p>
</li>
<li><p>Stateful widget&#x81F3;&#x5C11;&#x7531;&#x4E24;&#x4E2A;&#x7C7B;&#x7EC4;&#x6210;&#xFF1A;</p>
<ul>
<li>&#x4E00;&#x4E2A;<code>StatefulWidget</code>&#x7C7B;&#x3002;</li>
<li>&#x4E00;&#x4E2A; <code>State</code>&#x7C7B;&#xFF1B; <code>StatefulWidget</code>&#x7C7B;&#x672C;&#x8EAB;&#x662F;&#x4E0D;&#x53D8;&#x7684;&#xFF0C;&#x4F46;&#x662F;<code>State</code>&#x7C7B;&#x4E2D;&#x6301;&#x6709;&#x7684;&#x72B6;&#x6001;&#x5728;widget&#x751F;&#x547D;&#x5468;&#x671F;&#x4E2D;&#x53EF;&#x80FD;&#x4F1A;&#x53D1;&#x751F;&#x53D8;&#x5316;&#x3002;</li>
</ul>
<p><code>_MyHomePageState</code>&#x7C7B;&#x662F;<code>MyHomePage</code>&#x7C7B;&#x5BF9;&#x5E94;&#x7684;&#x72B6;&#x6001;&#x7C7B;&#x3002;&#x770B;&#x5230;&#x8FD9;&#x91CC;&#xFF0C;&#x8BFB;&#x8005;&#x53EF;&#x80FD;&#x5DF2;&#x7ECF;&#x53D1;&#x73B0;&#xFF1A;&#x548C;<code>MyApp</code> &#x7C7B;&#x4E0D;&#x540C;&#xFF0C; <code>MyHomePage</code>&#x7C7B;&#x4E2D;&#x5E76;&#x6CA1;&#x6709;<code>build</code>&#x65B9;&#x6CD5;&#xFF0C;&#x53D6;&#x800C;&#x4EE3;&#x4E4B;&#x7684;&#x662F;&#xFF0C;<code>build</code>&#x65B9;&#x6CD5;&#x88AB;&#x632A;&#x5230;&#x4E86;<code>_MyHomePageState</code>&#x65B9;&#x6CD5;&#x4E2D;&#xFF0C;&#x81F3;&#x4E8E;&#x4E3A;&#x4EC0;&#x4E48;&#x8FD9;&#x4E48;&#x505A;&#xFF0C;&#x5148;&#x7559;&#x4E2A;&#x7591;&#x95EE;&#xFF0C;&#x5728;&#x5206;&#x6790;&#x5B8C;&#x5B8C;&#x6574;&#x4EE3;&#x7801;&#x540E;&#x518D;&#x6765;&#x89E3;&#x7B54;&#x3002;</p>
</li>
</ol>
<h3 id="state&#x7C7B;">State&#x7C7B;</h3>
<p>&#x63A5;&#x4E0B;&#x6765;&#xFF0C;&#x6211;&#x4EEC;&#x770B;&#x770B;<code>_MyHomePageState</code>&#x4E2D;&#x90FD;&#x5305;&#x542B;&#x54EA;&#x4E9B;&#x4E1C;&#x897F;&#xFF1A;</p>
<ol>
<li><p>&#x8BE5;&#x7EC4;&#x4EF6;&#x7684;&#x72B6;&#x6001;&#x3002;&#x7531;&#x4E8E;&#x6211;&#x4EEC;&#x53EA;&#x9700;&#x8981;&#x7EF4;&#x62A4;&#x4E00;&#x4E2A;&#x70B9;&#x51FB;&#x6B21;&#x6570;&#x8BA1;&#x6570;&#x5668;&#xFF0C;&#x6240;&#x4EE5;&#x5B9A;&#x4E49;&#x4E00;&#x4E2A;<code>_counter</code>&#x72B6;&#x6001;&#xFF1A;</p>
<pre class="language-"><code class="lang-dart">int _counter <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> <span class="token comment">//&#x7528;&#x4E8E;&#x8BB0;&#x5F55;&#x6309;&#x94AE;&#x70B9;&#x51FB;&#x7684;&#x603B;&#x6B21;&#x6570;</span>
</code></pre>
<p><code>_counter</code> &#x4E3A;&#x4FDD;&#x5B58;&#x5C4F;&#x5E55;&#x53F3;&#x4E0B;&#x89D2;&#x5E26;&#x201C;+&#x201D;&#x53F7;&#x6309;&#x94AE;&#x70B9;&#x51FB;&#x6B21;&#x6570;&#x7684;&#x72B6;&#x6001;&#x3002;</p>
</li>
<li><p>&#x8BBE;&#x7F6E;&#x72B6;&#x6001;&#x7684;&#x81EA;&#x589E;&#x51FD;&#x6570;&#x3002;</p>
<pre class="language-"><code class="lang-dart"><span class="token keyword">void</span> <span class="token function">_incrementCounter</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token function">setState</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
     _counter<span class="token operator">++</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre>
<p>&#x5F53;&#x6309;&#x94AE;&#x70B9;&#x51FB;&#x65F6;&#xFF0C;&#x4F1A;&#x8C03;&#x7528;&#x6B64;&#x51FD;&#x6570;&#xFF0C;&#x8BE5;&#x51FD;&#x6570;&#x7684;&#x4F5C;&#x7528;&#x662F;&#x5148;&#x81EA;&#x589E;<code>_counter</code>&#xFF0C;&#x7136;&#x540E;&#x8C03;&#x7528;<code>setState</code> &#x65B9;&#x6CD5;&#x3002;<code>setState</code>&#x65B9;&#x6CD5;&#x7684;&#x4F5C;&#x7528;&#x662F;&#x901A;&#x77E5;Flutter&#x6846;&#x67B6;&#xFF0C;&#x6709;&#x72B6;&#x6001;&#x53D1;&#x751F;&#x4E86;&#x6539;&#x53D8;&#xFF0C;Flutter&#x6846;&#x67B6;&#x6536;&#x5230;&#x901A;&#x77E5;&#x540E;&#xFF0C;&#x4F1A;&#x6267;&#x884C;<code>build</code>&#x65B9;&#x6CD5;&#x6765;&#x6839;&#x636E;&#x65B0;&#x7684;&#x72B6;&#x6001;&#x91CD;&#x65B0;&#x6784;&#x5EFA;&#x754C;&#x9762;&#xFF0C; Flutter &#x5BF9;&#x6B64;&#x65B9;&#x6CD5;&#x505A;&#x4E86;&#x4F18;&#x5316;&#xFF0C;&#x4F7F;&#x91CD;&#x65B0;&#x6267;&#x884C;&#x53D8;&#x7684;&#x5F88;&#x5FEB;&#xFF0C;&#x6240;&#x4EE5;&#x4F60;&#x53EF;&#x4EE5;&#x91CD;&#x65B0;&#x6784;&#x5EFA;&#x4EFB;&#x4F55;&#x9700;&#x8981;&#x66F4;&#x65B0;&#x7684;&#x4E1C;&#x897F;&#xFF0C;&#x800C;&#x65E0;&#x9700;&#x5206;&#x522B;&#x53BB;&#x4FEE;&#x6539;&#x5404;&#x4E2A;widget&#x3002;</p>
</li>
<li><p>&#x6784;&#x5EFA;UI&#x754C;&#x9762;</p>
<p>&#x6784;&#x5EFA;UI&#x754C;&#x9762;&#x7684;&#x903B;&#x8F91;&#x5728;<code>build</code>&#x65B9;&#x6CD5;&#x4E2D;&#xFF0C;&#x5F53;<code>MyHomePage</code>&#x7B2C;&#x4E00;&#x6B21;&#x521B;&#x5EFA;&#x65F6;&#xFF0C;<code>_MyHomePageState</code>&#x7C7B;&#x4F1A;&#x88AB;&#x521B;&#x5EFA;&#xFF0C;&#x5F53;&#x521D;&#x59CB;&#x5316;&#x5B8C;&#x6210;&#x540E;&#xFF0C;Flutter&#x6846;&#x67B6;&#x4F1A;&#x8C03;&#x7528;Widget&#x7684;<code>build</code>&#x65B9;&#x6CD5;&#x6765;&#x6784;&#x5EFA;widget&#x6811;&#xFF0C;&#x6700;&#x7EC8;&#x5C06;widget&#x6811;&#x6E32;&#x67D3;&#x5230;&#x8BBE;&#x5907;&#x5C4F;&#x5E55;&#x4E0A;&#x3002;&#x6240;&#x4EE5;&#xFF0C;&#x6211;&#x4EEC;&#x770B;&#x770B;<code>_MyHomePageState</code>&#x7684;<code>build</code>&#x65B9;&#x6CD5;&#x4E2D;&#x90FD;&#x5E72;&#x4E86;&#x4EC0;&#x4E48;&#x4E8B;&#xFF1A;</p>
<pre class="language-"><code class="lang-dart">  Widget <span class="token function">build</span><span class="token punctuation">(</span>BuildContext context<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> <span class="token keyword">new</span> <span class="token class-name">Scaffold</span><span class="token punctuation">(</span>
      appBar<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">AppBar</span><span class="token punctuation">(</span>
        title<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">Text</span><span class="token punctuation">(</span>widget<span class="token punctuation">.</span>title<span class="token punctuation">)</span><span class="token punctuation">,</span>
      <span class="token punctuation">)</span><span class="token punctuation">,</span>
      body<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">Center</span><span class="token punctuation">(</span>
        child<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">Column</span><span class="token punctuation">(</span>
          mainAxisAlignment<span class="token punctuation">:</span> MainAxisAlignment<span class="token punctuation">.</span>center<span class="token punctuation">,</span>
          children<span class="token punctuation">:</span> <span class="token operator">&lt;</span>Widget<span class="token operator">&gt;</span><span class="token punctuation">[</span>
            <span class="token keyword">new</span> <span class="token class-name">Text</span><span class="token punctuation">(</span>
              <span class="token string">&apos;You have pushed the button this many times:&apos;</span><span class="token punctuation">,</span>
            <span class="token punctuation">)</span><span class="token punctuation">,</span>
            <span class="token keyword">new</span> <span class="token class-name">Text</span><span class="token punctuation">(</span>
              <span class="token string">&apos;$_counter&apos;</span><span class="token punctuation">,</span>
              style<span class="token punctuation">:</span> Theme<span class="token punctuation">.</span><span class="token function">of</span><span class="token punctuation">(</span>context<span class="token punctuation">)</span><span class="token punctuation">.</span>textTheme<span class="token punctuation">.</span>display1<span class="token punctuation">,</span>
            <span class="token punctuation">)</span><span class="token punctuation">,</span>
          <span class="token punctuation">]</span><span class="token punctuation">,</span>
        <span class="token punctuation">)</span><span class="token punctuation">,</span>
      <span class="token punctuation">)</span><span class="token punctuation">,</span>
      floatingActionButton<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">FloatingActionButton</span><span class="token punctuation">(</span>
        onPressed<span class="token punctuation">:</span> _incrementCounter<span class="token punctuation">,</span>
        tooltip<span class="token punctuation">:</span> <span class="token string">&apos;Increment&apos;</span><span class="token punctuation">,</span>
        child<span class="token punctuation">:</span> <span class="token keyword">new</span> <span class="token class-name">Icon</span><span class="token punctuation">(</span>Icons<span class="token punctuation">.</span>add<span class="token punctuation">)</span><span class="token punctuation">,</span>
      <span class="token punctuation">)</span><span class="token punctuation">,</span>
    <span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
</code></pre>
<ul>
<li><code>Scaffold</code> &#x662F; Material &#x5E93;&#x4E2D;&#x63D0;&#x4F9B;&#x7684;&#x9875;&#x9762;&#x811A;&#x624B;&#x67B6;&#xFF0C;&#x5B83;&#x63D0;&#x4F9B;&#x4E86;&#x9ED8;&#x8BA4;&#x7684;&#x5BFC;&#x822A;&#x680F;&#x3001;&#x6807;&#x9898;&#x548C;&#x5305;&#x542B;&#x4E3B;&#x5C4F;&#x5E55;widget&#x6811;&#xFF08;&#x540E;&#x540C;&#x201C;&#x7EC4;&#x4EF6;&#x6811;&#x201D;&#x6216;&#x201C;&#x90E8;&#x4EF6;&#x6811;&#x201D;&#xFF09;&#x7684;<code>body</code>&#x5C5E;&#x6027;&#xFF0C;&#x7EC4;&#x4EF6;&#x6811;&#x53EF;&#x4EE5;&#x5F88;&#x590D;&#x6742;&#x3002;&#x672C;&#x4E66;&#x540E;&#x9762;&#x793A;&#x4F8B;&#x4E2D;&#xFF0C;&#x8DEF;&#x7531;&#x9ED8;&#x8BA4;&#x90FD;&#x662F;&#x901A;&#x8FC7;<code>Scaffold</code>&#x521B;&#x5EFA;&#x3002;</li>
<li><code>body</code>&#x7684;&#x7EC4;&#x4EF6;&#x6811;&#x4E2D;&#x5305;&#x542B;&#x4E86;&#x4E00;&#x4E2A;<code>Center</code> &#x7EC4;&#x4EF6;&#xFF0C;<code>Center</code> &#x53EF;&#x4EE5;&#x5C06;&#x5176;&#x5B50;&#x7EC4;&#x4EF6;&#x6811;&#x5BF9;&#x9F50;&#x5230;&#x5C4F;&#x5E55;&#x4E2D;&#x5FC3;&#x3002;&#x6B64;&#x4F8B;&#x4E2D;&#xFF0C; <code>Center</code> &#x5B50;&#x7EC4;&#x4EF6;&#x662F;&#x4E00;&#x4E2A;<code>Column</code> &#x7EC4;&#x4EF6;&#xFF0C;<code>Column</code>&#x7684;&#x4F5C;&#x7528;&#x662F;&#x5C06;&#x5176;&#x6240;&#x6709;&#x5B50;&#x7EC4;&#x4EF6;&#x6CBF;&#x5C4F;&#x5E55;&#x5782;&#x76F4;&#x65B9;&#x5411;&#x4F9D;&#x6B21;&#x6392;&#x5217;&#xFF1B; &#x6B64;&#x4F8B;&#x4E2D;<code>Column</code>&#x5B50;&#x7EC4;&#x4EF6;&#x662F;&#x4E24;&#x4E2A; <code>Text</code>&#xFF0C;&#x7B2C;&#x4E00;&#x4E2A;<code>Text</code> &#x663E;&#x793A;&#x56FA;&#x5B9A;&#x6587;&#x672C; &#x201C;You have pushed the button this many times:&#x201D;&#xFF0C;&#x7B2C;&#x4E8C;&#x4E2A;<code>Text</code> &#x663E;&#x793A;<code>_counter</code>&#x72B6;&#x6001;&#x7684;&#x6570;&#x503C;&#x3002;</li>
<li><code>floatingActionButton</code>&#x662F;&#x9875;&#x9762;&#x53F3;&#x4E0B;&#x89D2;&#x7684;&#x5E26;&#x201C;+&#x201D;&#x7684;&#x60AC;&#x6D6E;&#x6309;&#x94AE;&#xFF0C;&#x5B83;&#x7684;<code>onPressed</code>&#x5C5E;&#x6027;&#x63A5;&#x53D7;&#x4E00;&#x4E2A;&#x56DE;&#x8C03;&#x51FD;&#x6570;&#xFF0C;&#x4EE3;&#x8868;&#x5B83;&#x88AB;&#x70B9;&#x51FB;&#x540E;&#x7684;&#x5904;&#x7406;&#x5668;&#xFF0C;&#x672C;&#x4F8B;&#x4E2D;&#x76F4;&#x63A5;&#x5C06;<code>_incrementCounter</code>&#x65B9;&#x6CD5;&#x4F5C;&#x4E3A;&#x5176;&#x5904;&#x7406;&#x51FD;&#x6570;&#x3002;</li>
</ul>
</li>
</ol>
<p>&#x73B0;&#x5728;&#xFF0C;&#x6211;&#x4EEC;&#x5C06;&#x6574;&#x4E2A;&#x8BA1;&#x6570;&#x5668;&#x6267;&#x884C;&#x6D41;&#x7A0B;&#x4E32;&#x8D77;&#x6765;&#xFF1A;&#x5F53;&#x53F3;&#x4E0B;&#x89D2;&#x7684;<code>floatingActionButton</code>&#x6309;&#x94AE;&#x88AB;&#x70B9;&#x51FB;&#x4E4B;&#x540E;&#xFF0C;&#x4F1A;&#x8C03;&#x7528;<code>_incrementCounter</code>&#x65B9;&#x6CD5;&#x3002;&#x5728;<code>_incrementCounter</code>&#x65B9;&#x6CD5;&#x4E2D;&#xFF0C;&#x9996;&#x5148;&#x4F1A;&#x81EA;&#x589E;<code>_counter</code>&#x8BA1;&#x6570;&#x5668;&#xFF08;&#x72B6;&#x6001;&#xFF09;&#xFF0C;&#x7136;&#x540E;<code>setState</code>&#x4F1A;&#x901A;&#x77E5;Flutter&#x6846;&#x67B6;&#x72B6;&#x6001;&#x53D1;&#x751F;&#x53D8;&#x5316;&#xFF0C;&#x63A5;&#x7740;&#xFF0C;Flutter&#x6846;&#x67B6;&#x4F1A;&#x8C03;&#x7528;<code>build</code>&#x65B9;&#x6CD5;&#x4EE5;&#x65B0;&#x7684;&#x72B6;&#x6001;&#x91CD;&#x65B0;&#x6784;&#x5EFA;UI&#xFF0C;&#x6700;&#x7EC8;&#x663E;&#x793A;&#x5728;&#x8BBE;&#x5907;&#x5C4F;&#x5E55;&#x4E0A;&#x3002;</p>
<h4 id="&#x4E3A;&#x4EC0;&#x4E48;&#x8981;&#x5C06;build&#x65B9;&#x6CD5;&#x653E;&#x5728;state&#x4E2D;&#xFF0C;&#x800C;&#x4E0D;&#x662F;&#x653E;&#x5728;statefulwidget&#x4E2D;&#xFF1F;">&#x4E3A;&#x4EC0;&#x4E48;&#x8981;&#x5C06;build&#x65B9;&#x6CD5;&#x653E;&#x5728;State&#x4E2D;&#xFF0C;&#x800C;&#x4E0D;&#x662F;&#x653E;&#x5728;StatefulWidget&#x4E2D;&#xFF1F;</h4>
<p>&#x73B0;&#x5728;&#xFF0C;&#x6211;&#x4EEC;&#x56DE;&#x7B54;&#x4E4B;&#x524D;&#x63D0;&#x51FA;&#x7684;&#x95EE;&#x9898;&#xFF0C;&#x4E3A;&#x4EC0;&#x4E48;<code>build()</code>&#x65B9;&#x6CD5;&#x653E;&#x5728;State&#xFF08;&#x800C;&#x4E0D;&#x662F;<code>StatefulWidget</code>&#xFF09;&#x4E2D; &#xFF1F;&#x8FD9;&#x4E3B;&#x8981;&#x662F;&#x4E3A;&#x4E86;&#x63D0;&#x9AD8;&#x5F00;&#x53D1;&#x7684;&#x7075;&#x6D3B;&#x6027;&#x3002;&#x5982;&#x679C;&#x5C06;<code>build()</code>&#x65B9;&#x6CD5;&#x653E;&#x5728;<code>StatefulWidget</code>&#x4E2D;&#x5219;&#x4F1A;&#x6709;&#x4E24;&#x4E2A;&#x95EE;&#x9898;&#xFF1A;</p>
<ul>
<li><p>&#x72B6;&#x6001;&#x8BBF;&#x95EE;&#x4E0D;&#x4FBF;</p>
<p>&#x8BD5;&#x60F3;&#x4E00;&#x4E0B;&#xFF0C;&#x5982;&#x679C;&#x6211;&#x4EEC;&#x7684;<code>StatefulWidget</code>&#x6709;&#x5F88;&#x591A;&#x72B6;&#x6001;&#xFF0C;&#x800C;&#x6BCF;&#x6B21;&#x72B6;&#x6001;&#x6539;&#x53D8;&#x90FD;&#x8981;&#x8C03;&#x7528;<code>build</code>&#x65B9;&#x6CD5;&#xFF0C;&#x7531;&#x4E8E;&#x72B6;&#x6001;&#x662F;&#x4FDD;&#x5B58;&#x5728;State&#x4E2D;&#x7684;&#xFF0C;&#x5982;&#x679C;<code>build</code>&#x65B9;&#x6CD5;&#x5728;<code>StatefulWidget</code>&#x4E2D;&#xFF0C;&#x90A3;&#x4E48;<code>build</code>&#x65B9;&#x6CD5;&#x548C;&#x72B6;&#x6001;&#x5206;&#x522B;&#x5728;&#x4E24;&#x4E2A;&#x7C7B;&#x4E2D;&#xFF0C;&#x90A3;&#x4E48;&#x6784;&#x5EFA;&#x65F6;&#x8BFB;&#x53D6;&#x72B6;&#x6001;&#x5C06;&#x4F1A;&#x5F88;&#x4E0D;&#x65B9;&#x4FBF;&#xFF01;&#x8BD5;&#x60F3;&#x4E00;&#x4E0B;&#xFF0C;&#x5982;&#x679C;&#x771F;&#x7684;&#x5C06;<code>build</code>&#x65B9;&#x6CD5;&#x653E;&#x5728;StatefulWidget&#x4E2D;&#x7684;&#x8BDD;&#xFF0C;&#x7531;&#x4E8E;&#x6784;&#x5EFA;&#x7528;&#x6237;&#x754C;&#x9762;&#x8FC7;&#x7A0B;&#x9700;&#x8981;&#x4F9D;&#x8D56;State&#xFF0C;&#x6240;&#x4EE5;<code>build</code>&#x65B9;&#x6CD5;&#x5C06;&#x5FC5;&#x987B;&#x52A0;&#x4E00;&#x4E2A;<code>State</code>&#x53C2;&#x6570;&#xFF0C;&#x5927;&#x6982;&#x662F;&#x4E0B;&#x9762;&#x8FD9;&#x6837;&#xFF1A;</p>
<pre class="language-"><code class="lang-dart">  Widget <span class="token function">build</span><span class="token punctuation">(</span>BuildContext context<span class="token punctuation">,</span> State state<span class="token punctuation">)</span><span class="token punctuation">{</span>
      <span class="token comment">//state.counter</span>
      <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
  <span class="token punctuation">}</span>
</code></pre>
<p>&#x8FD9;&#x6837;&#x7684;&#x8BDD;&#x5C31;&#x53EA;&#x80FD;&#x5C06;State&#x7684;&#x6240;&#x6709;&#x72B6;&#x6001;&#x58F0;&#x660E;&#x4E3A;&#x516C;&#x5F00;&#x7684;&#x72B6;&#x6001;&#xFF0C;&#x8FD9;&#x6837;&#x624D;&#x80FD;&#x5728;State&#x7C7B;&#x5916;&#x90E8;&#x8BBF;&#x95EE;&#x72B6;&#x6001;&#xFF01;&#x4F46;&#x662F;&#xFF0C;&#x5C06;&#x72B6;&#x6001;&#x8BBE;&#x7F6E;&#x4E3A;&#x516C;&#x5F00;&#x540E;&#xFF0C;&#x72B6;&#x6001;&#x5C06;&#x4E0D;&#x518D;&#x5177;&#x6709;&#x79C1;&#x5BC6;&#x6027;&#xFF0C;&#x8FD9;&#x5C31;&#x4F1A;&#x5BFC;&#x81F4;&#x5BF9;&#x72B6;&#x6001;&#x7684;&#x4FEE;&#x6539;&#x5C06;&#x4F1A;&#x53D8;&#x7684;&#x4E0D;&#x53EF;&#x63A7;&#x3002;&#x4F46;&#x5982;&#x679C;&#x5C06;<code>build()</code>&#x65B9;&#x6CD5;&#x653E;&#x5728;State&#x4E2D;&#x7684;&#x8BDD;&#xFF0C;&#x6784;&#x5EFA;&#x8FC7;&#x7A0B;&#x4E0D;&#x4EC5;&#x53EF;&#x4EE5;&#x76F4;&#x63A5;&#x8BBF;&#x95EE;&#x72B6;&#x6001;&#xFF0C;&#x800C;&#x4E14;&#x4E5F;&#x65E0;&#x9700;&#x516C;&#x5F00;&#x79C1;&#x6709;&#x72B6;&#x6001;&#xFF0C;&#x8FD9;&#x4F1A;&#x975E;&#x5E38;&#x65B9;&#x4FBF;&#x3002;</p>
</li>
<li><p>&#x7EE7;&#x627F;<code>StatefulWidget</code>&#x4E0D;&#x4FBF;</p>
<p>&#x4F8B;&#x5982;&#xFF0C;Flutter&#x4E2D;&#x6709;&#x4E00;&#x4E2A;&#x52A8;&#x753B;widget&#x7684;&#x57FA;&#x7C7B;<code>AnimatedWidget</code>&#xFF0C;&#x5B83;&#x7EE7;&#x627F;&#x81EA;<code>StatefulWidget</code>&#x7C7B;&#x3002;<code>AnimatedWidget</code>&#x4E2D;&#x5F15;&#x5165;&#x4E86;&#x4E00;&#x4E2A;&#x62BD;&#x8C61;&#x65B9;&#x6CD5;<code>build(BuildContext context)</code>&#xFF0C;&#x7EE7;&#x627F;&#x81EA;<code>AnimatedWidget</code>&#x7684;&#x52A8;&#x753B;widget&#x90FD;&#x8981;&#x5B9E;&#x73B0;&#x8FD9;&#x4E2A;<code>build</code>&#x65B9;&#x6CD5;&#x3002;&#x73B0;&#x5728;&#x8BBE;&#x60F3;&#x4E00;&#x4E0B;&#xFF0C;&#x5982;&#x679C;<code>StatefulWidget</code> &#x7C7B;&#x4E2D;&#x5DF2;&#x7ECF;&#x6709;&#x4E86;&#x4E00;&#x4E2A;<code>build</code>&#x65B9;&#x6CD5;&#xFF0C;&#x6B63;&#x5982;&#x4E0A;&#x9762;&#x6240;&#x8FF0;&#xFF0C;&#x6B64;&#x65F6;<code>build</code>&#x65B9;&#x6CD5;&#x9700;&#x8981;&#x63A5;&#x6536;&#x4E00;&#x4E2A;state&#x5BF9;&#x8C61;&#xFF0C;&#x8FD9;&#x5C31;&#x610F;&#x5473;&#x7740;<code>AnimatedWidget</code>&#x5FC5;&#x987B;&#x5C06;&#x81EA;&#x5DF1;&#x7684;State&#x5BF9;&#x8C61;(&#x8BB0;&#x4E3A;_animatedWidgetState)&#x63D0;&#x4F9B;&#x7ED9;&#x5176;&#x5B50;&#x7C7B;&#xFF0C;&#x56E0;&#x4E3A;&#x5B50;&#x7C7B;&#x9700;&#x8981;&#x5728;&#x5176;<code>build</code>&#x65B9;&#x6CD5;&#x4E2D;&#x8C03;&#x7528;&#x7236;&#x7C7B;&#x7684;<code>build</code>&#x65B9;&#x6CD5;&#xFF0C;&#x4EE3;&#x7801;&#x53EF;&#x80FD;&#x5982;&#x4E0B;&#xFF1A;</p>
<pre class="language-"><code class="lang-dart"><span class="token keyword">class</span> <span class="token class-name">MyAnimationWidget</span> <span class="token keyword">extends</span> <span class="token class-name">AnimatedWidget</span><span class="token punctuation">{</span>
    <span class="token metadata symbol">@override</span>
    Widget <span class="token function">build</span><span class="token punctuation">(</span>BuildContext context<span class="token punctuation">,</span> State state<span class="token punctuation">)</span><span class="token punctuation">{</span>
      <span class="token comment">//&#x7531;&#x4E8E;&#x5B50;&#x7C7B;&#x8981;&#x7528;&#x5230;AnimatedWidget&#x7684;&#x72B6;&#x6001;&#x5BF9;&#x8C61;_animatedWidgetState&#xFF0C;</span>
      <span class="token comment">//&#x6240;&#x4EE5;AnimatedWidget&#x5FC5;&#x987B;&#x901A;&#x8FC7;&#x67D0;&#x79CD;&#x65B9;&#x5F0F;&#x5C06;&#x5176;&#x72B6;&#x6001;&#x5BF9;&#x8C61;_animatedWidgetState</span>
      <span class="token comment">//&#x66B4;&#x9732;&#x7ED9;&#x5176;&#x5B50;&#x7C7B;   </span>
      <span class="token keyword">super</span><span class="token punctuation">.</span><span class="token function">build</span><span class="token punctuation">(</span>context<span class="token punctuation">,</span> _animatedWidgetState<span class="token punctuation">)</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre>
<p>&#x8FD9;&#x6837;&#x5F88;&#x663E;&#x7136;&#x662F;&#x4E0D;&#x5408;&#x7406;&#x7684;&#xFF0C;&#x56E0;&#x4E3A;</p>
<ol>
<li><code>AnimatedWidget</code>&#x7684;&#x72B6;&#x6001;&#x5BF9;&#x8C61;&#x662F;<code>AnimatedWidget</code>&#x5185;&#x90E8;&#x5B9E;&#x73B0;&#x7EC6;&#x8282;&#xFF0C;&#x4E0D;&#x5E94;&#x8BE5;&#x66B4;&#x9732;&#x7ED9;&#x5916;&#x90E8;&#x3002;</li>
<li>&#x5982;&#x679C;&#x8981;&#x5C06;&#x7236;&#x7C7B;&#x72B6;&#x6001;&#x66B4;&#x9732;&#x7ED9;&#x5B50;&#x7C7B;&#xFF0C;&#x90A3;&#x4E48;&#x5FC5;&#x987B;&#x5F97;&#x6709;&#x4E00;&#x79CD;&#x4F20;&#x9012;&#x673A;&#x5236;&#xFF0C;&#x800C;&#x505A;&#x8FD9;&#x4E00;&#x5957;&#x4F20;&#x9012;&#x673A;&#x5236;&#x662F;&#x65E0;&#x610F;&#x4E49;&#x7684;&#xFF0C;&#x56E0;&#x4E3A;&#x7236;&#x5B50;&#x7C7B;&#x4E4B;&#x95F4;&#x72B6;&#x6001;&#x7684;&#x4F20;&#x9012;&#x548C;&#x5B50;&#x7C7B;&#x672C;&#x8EAB;&#x903B;&#x8F91;&#x662F;&#x65E0;&#x5173;&#x7684;&#x3002;</li>
</ol>
</li>
</ul>
<p>&#x7EFC;&#x4E0A;&#x6240;&#x8FF0;&#xFF0C;&#x53EF;&#x4EE5;&#x53D1;&#x73B0;&#xFF0C;&#x5BF9;&#x4E8E;<code>StatefulWidget</code>&#xFF0C;&#x5C06;<code>build</code>&#x65B9;&#x6CD5;&#x653E;&#x5728;State&#x4E2D;&#xFF0C;&#x53EF;&#x4EE5;&#x7ED9;&#x5F00;&#x53D1;&#x5E26;&#x6765;&#x5F88;&#x5927;&#x7684;&#x7075;&#x6D3B;&#x6027;&#x3002;</p>

                                
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